The investigators aim to study the effect of SOT in highlanders with high altitude pulmonary hypertension (HAPH) who permanently live >2500m on 6-minute walk distance (6MWD) assessed at 3200m.

Highlanders with HAPH diagnosed by echocardiography and defined by a RV/RA (Tricuspid Regurgitation Pressure Gradient) >30 mmHg will be recruited for this project. Highlanders permanently living at HA >2500 m will perform a 6-minute walk distance test near their living altitude in Aksay at 3200 m with and without portable pulsed supplemental oxygen therapy (SOT) via nasal cannula according to a randomized cross-over design.

Inclusion Criteria:

• Permanently living >2500 m
• HAPH diagnosed with a minimum RV/RA of 30 mmHg assessed by echocardiography at an altitude of 3200 m
• Written informed consent

Exclusion Criteria:

• Highlanders who cannot follow the study investigations,
• Patients with moderate to severe concomitant lung disease (FEV1<70% or forced vital capacity <70%), severe parenchymal lung disease, heavy smoking >20 cigarettes/day or >20 pack-years.
• Coexistent unstable systemic hypertension or coronary artery disease that required adjustment of medication within the last 2 months
• Regular use of medication that affects control of breathing (benzodiazepines, opioids, acetazolamide)